The present invention relates to vehicle driving apparatuses, and, more particularly, to vehicle driving apparatuses that selectively connect a motor generator to an engine.
Japanese Unexamined Patent Publication Nos. 11-147424 and 9-324668 describe a vehicle driving apparatus that connects a motor generator to an engine through a power distributing mechanism, or a pulley and a belt. The power distributing mechanism also connects the motor generator to auxiliary devices such as an air-conditioning compressor and a power steering pump. The power distributing mechanism is connected to the engine drive shaft through a clutch.
When the vehicle is traveling in a normal operation mode, the clutch is engaged with the power distributing mechanism such that the motor generator generates power in accordance with the power of the engine. The engine may include an economy running system or an automatic stop system. The system automatically stops the engine when, for example, the vehicle stops at a signal and automatically re-starts the engine when the vehicle is operated to re-start, thus lowering power consumption. When the engine is automatically re-started by this system, the power distributing mechanism is engaged with the clutch such that the motor generator activates the engine.
When the economy running system automatically stops the engine, the clutch is released such that the motor generator drives the auxiliary devices without rotating the engine drive shaft. That is, the motor generator is selectively connected to the engine, thus improving the efficiency of the motor generator.
However, the operation efficiency of the motor generator can still be improved. In other words, the motor generator can be operated more efficiently to improve the vehicle's performance.